When it comes to thick, healthy hair, the most important diet-related step you can take is to fill your plate with mostly plant-based foods. Follow a Mediterranean-style plan and regularly eat protein from nutrient-dense sources, fiber-filled veggies and fruit, 100% whole grains, and healthy fats from nuts, seeds, and plant-based oils. A balanced diet will help you get enough of the key nutrients that keep skin, hair, and nails in great shape.